const mixin = {
  say() {
    console.log(`${this.name}在说话`);
  },
  sing() {
    console.log(`${this.name}在唱歌`);
  },
  run() {
    console.log(`${this.name}在跑步`);
  }
}
// 没有任何方法
class Student {
  constructor(name) {
    this.name = name;
  }
}
// 拷贝不通过集成去扩展方法
Object.assign(Student.prototype, mixin);
const student = new Student('王二住');
student.run();
console.log('--------student', student, mixin)